Condition before being touched

So here's the deal people, I have an old Avenger 350 4X4 Shaft Driven ATV. They only made them in the early 80's their thought of as the first four wheelers from around back when Suzuki made one in 1982. I believe the engine on it is a Kohler as I watched this video https://www.bing.com/videos/search?q=avenger+400+atv&view=detail&mid=1E10E939019CA07770031E10E939019CA0777003&FORM=VIRE but mine is a 350. That's if its original, and it all looks original. I am wondering where I can get parts for this engine, or really what engine is it. I have no way to find the year, unless you guys know where a serial number might be. Every sticker is worn off. IF anyone has any information at all on these old wheelers it would be greatly appreciated. I specifically need the gaskets for the carb, and don't tell me I could build them please I want to restore it as perfectly as I can. I can take pictures of the wheeler/carb if it'll help. Let me know.

My old Big Bear nearly left me stranded but I managed to limp back to my garage just before it died. Now No Spark. I’ve changed the obvious, inexpensive and easy parts- spark plug & coil without any luck. 
Ive stripped it down and traced all of the related wiring, checking as many connections as I can but no luck again. 
Next I pulled the cover and accessed the stator housing to inspect and do some resistance testing to ID a possible short. 
Here are my readings:
Source coil- 325 ohms
Pickup coil- 225
Can anyone tell me if these are good numbers, and if good, where to go next?
I assume my next purchase will either be a new stator or CDI, but since neither of these tend to be returnable items I want to be as sure as I can I’m gonna get a resolution to the problem!!
Thanks,
Gary in SC

Ok i am not quick to jump on a forum and post a question without doing my own part and trying to research and solve the problem myself but I cannot find any definitive information anywhere about my problem. I have a Big Bear 350 that I picked up very cheap which had been sitting in a field for years. I am not new to building wheelers but this one has me beat. After rebuilding top end and replacing the carb it fires right up. The vin has some number worn off from being next to the shifter but from the parts in the clutch i assume it is early since 87 parts seem to be the only ones that match. Thats when the plot thickened. 
Reverse works fine but when in the forward gears it would not go past 1st and was hard to get into neutral. ie. a it took a million clicks up to thump into 1 and as many down to find neutral. still never getting past 1st. within minutes i could hear metal screeching and whirling around in the clutch side of the motor. I took the cover off to find that 3 out of the 4 springs on the centrifugal clutch had broken and were shredded. Also the black mechanism that the pawl on shift shaft grabs moves was loose so it wasnt always grab to change the gear on the transmission. I tightened that mech, and replaced the springs assuming it would solve the problem since the gears were not actually changing from the lever and the carrier should obviously not only have 1 spring left. 
After putting everything back together it did go into 1st fairly easy but then i again couldnt get it back to N without a million clicks down and couldnt get it to go past 1st. I did one time get it into a higher gear who knows what one but i gained some speed and dropped rpm.
If i jack both the front and the back wheels off the ground and run the motor it becomes much easier to shift and i can get it to run through the gears pretty well. Usually going into N without a huge fight. not perfect but it does hit neutral and roar while spinning the wheels instead of gain rpm and with the power. 
I have tried every possible position on the clutch adjustment screw without any noticeable result. I think this could potentially be where my problem lies at this point.
does anyone know if the case is supposed to be threaded? because mine is not. obviously it seems as though it should be since every other bike ive touched has been. i even took the cover off my quadrunner to make sure it wasnt crazy.
when the screw is adjusted and the jam nut tightened the screw will just slide back out since there is no threading in the case. accomplishing nothing. 
 
Does anyone have any insight on any of this? Are my plates stuck, Centrif clutch worn out, case stripped or something else crazy im over looking? 
 

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Introducing the 2020 Yamaha XT-R editions of ATV and Side-by-Side vehicles featuring exclusive XT-R features like a factory-installed Warn Winch, advanced suspension, special-edition paint and color-matched wheels with extreme terrain tires, all Assembled in the USA for unmatched Proven Off-Road capability, comfort, and confidence. 
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